1-aminocyclopropane-1-carboxylate synthase (ACS) enzymes catalyze the conversion of S-adenosyl-L-methionine (SAM) into 1-aminocyclopropane-1-carboxylate (ACC), a direct precursor of ethylene. (EC:4.4.1.14). Synonymes: S-adenosyl-L-methionine methylthioadenosine-lyase 7.